THIS INVENTION relates to measuring twist due to torque in a rotating shaft. It relates more specifically to a method of and measuring apparatus for measuring twist in a rotating shaft subjected to torque, to a method of and a measuring apparatus for measuring torque in a rotating shaft, and to a method of and an apparatus for managing operation of an engine.
International Patent Document WO 96/20395 discloses a process and device for determining a power output rate between a rotary shaft and one or more stationary machines connected to the shaft. The shaft is subjected to torque causing torsional deformation which is measured as an angle. Power output is determined as the product of the angle and a predetermined calibration coefficient.
International Patent Document WO 96/20395 discloses a process and device for determining a power output rate between a rotary shaft and one or more stationary machines connected to the shaft The shaft is subjected to torque causing torsional deformation which is measured as an angle, Power output is determined as the product of the angle and a predetermined calibration coefficient.
The term xe2x80x9ctwistxe2x80x9d is for convenience used for purposes of this invention to denote angular deflection or angular deformation.
In accordance with a first aspect of this invention, broadly, there is provided a method of measuring twist in a rotating shaft which is subjected to torque including sensing an arrival time moment of a measure point an the shaft at a fixed measure station, comparing the arrival time moment with a computed arrival time moment of said measure point at said measure station under a no load condition, measuring rotational speed of the shaft, and calculating the twist in the shaft on the basis of the time lag and the rotational speed.
The method may include sensing and recording a datum time moment when a datum point on the shaft, longitudinally spaced from said measure point by a predetermined distance, passes a fixed datum station, and measuring a measure time period between said datum time moment and said arrival time moment.
The method may include empirically predetermining a datum time period between a datum time moment and an arrival time moment under a no load condition at a determined rotational speed, and computing a computed time period and a computed arrival time moment for any specific rotational speed on the basis of the datum time period bearing in mind the respective rotational speeds.
In accordance with the first aspect of this invention, more specifically, there is provided method of measuring twist in a rotating shaft which is subjected to torque, between a datum point on the shaft and a measure point on the shaft longitudinally spaced from the datum point, the method Including
establishing a datum time period between a datum time moment the datum point passes a stationary datum station and a time moment the measure point passes a stationary measure station under a no load condition and recording rotational speed of the shaft as the datum speed;
measuring a measure time period between a time moment the datum point passes the stationary datum station and a time moment the measure point passes the stationary measure station when the shaft is subjected to torque, recording the rotational speed of the shaft as the measure speed and establishing longitudinal positions respectively at which torque is applied and of the datum point and of the measure point;
calculating the twist in the shaft from the difference between the measure time period and the datum time period, bearing in mind the difference between the measure speed and the datum speed.
A torque point at which torque is applied to the shaft and a load point at which a load is connected to the shaft may be longitudinally spaced, the shaft being stressed and undergoing twist between the torque point and the load point, one of the measure point and the datum point being positioned along said stressed portion of the shaft, the other of the measure point and the datum point being positioned in a relaxed portion of the shaft beyond one of the torque point and the load point.
Advantageously, the method may be applied to a shaft in the form of a crankshaft of a reciprocating internal combustion engine. The reciprocating engine may include a ring gear having gear teeth at one end of the crankshaft and a disc at an opposed end of the crankshaft, the datum point being on the disc, the measure point being on a gear tooth of the ring gear. The method is preferably performed in respect of a plurality of measure points and a plurality of datum points, the plurality of measure points being on a corresponding plurality of gear teeth of the ring gear and the plurality of datum points being points which are circumferentially spaced on the disc. Advantageously, the number of datum points and the number of measure points may be equal, to allow the respective datum points and measure points to be associated on a one-on-one basis.
When the reciprocating internal combustion engine includes a plurality of cylinders, the method may be performed in respect of each cylinder. Furthermore, the method may be performed for each power stroke of the reciprocating internal combustion engine.
In another technical application, the method may be applied to a gas turbine engine, the shaft then being a main shaft of the gas turbine engine.
Then, at least one of the datum point and the measure point may be on a vane of at least one of a compressor and a turbine of the gas turbine engine. However, the method is preferably performed in respect of a plurality of measure points and a pluralite of datum points, the plurality of measure points being an a corresponding plurality of vanes of one of the compressor and the turbine and the plurality of datum points being on a corresponding plurality of vanes of the other of the compressor and the turbine, the sensors being external of casings surrounding respectively the compressor and the turbine.
Generally, establishing the time moments may include triggering a sensor at respectively the datum station and the measure station by means of triggers at correspondingly the or each datum point and the or each measure point, creating a signal by each sensor and recording the signal against time.
The triggers may be masses of magnetic material, and the sensors may be responsive to said magnetic material to create said signals.
Instead, the triggers may be optically detectable surfaces, the sensors then sensing passing of the triggers optically.
In accordance with a second aspect of this invention, there is provided measuring apparatus for measuring twist in a rotating shaft which is subjected to torque, the measuring apparatus including
at least one datum trigger at a datum point on the shaft;
a datum sensor at a stationary datum station arranged to sense said at least one datum trigger when said at least one datum point is in register with the datum station and to generate correspondingly at least one datum signal;
at least one measure trigger at correspondingly at least one measure point on the haft longitudinally spaced from said at least one datum point;
a measure sensor at a stationary measure station arranged to sense said at least one measure trigger when said at least one measure trigger is in register with the measure station and to generate correspondingly at least one measure signal;
a clock keeping time;
a rotational speed meter for measuring and recording rotational speeds of the shaft against time respectively as the datum speed and as the measure speed;
recording means for recording said datum and measure signals against time;
a processor programmed to establish
correspondingly at least one datum time period between a time moment said at least one datum point passes the datum station and a time moment said at least one measure point passes the measure station under no load conditions and recording the rotational speed of the shaft as the datum speed,
correspondingly at least one measure time period between a time moment said at least one datum point passes the stationary datum station and a time moment said at least one measure point passes the stationary measur station when the shaft is subjected to torque and recording the rotational speed of the shaft as the measure speed, and
the twist of the shaft from the difference between said at least one measure time period and said at least one datum time period, bearing in mind the ratio between the measure speed and the datum speed.
The shaft may include a torque point at which torque is applied to the shaft in use and a load point at which a load is connected to the shaft in use, the torque point and the load point being longitudinally spaced, the shaft, in use, being stressed and undergoing twist between the torque point and the load point, one of the or each measure point and the or each datum point being positioned along said stressed portion of the shaft, the other of the or each measure point and the or each datum point being positioned in a relaxed portion of the shaft beyond one of the torque point and the lad point.
The shaft may advantageously be a crankshaft of a reciprocating internal combustion engine. Then the measuring apparatus may preferably include a plurality of measure points and a plurality of datum points.
Advantageously, the reciprocating engine may include a ring gear having gear teeth at one end of the crankshaft and a disc at an opposed end of the crankshaft, the datum points and the measuring points being respectively on gear teeth of the ring gear and at circumferentially spaced positions on the disc.
In another technical application, the shaft may be a main shaft of a gas turbine engine. Then, at least one of the datum point and the measure point is on correspondingly at least one of a vane of a compressor and a vane of a turbine of the gas turbine engine. However, the measuring apparatus may include a plurality of datum points and a plurality of measure points, the datum points and the measure points being respectively on vanes of the compressor and the turbine.
The triggers may be masses of magnetic material, and the sensors may be magnetic sensors responsive to said magnetic material to generate signals. The magnetic sensors may be arranged externally of casings surrounding respectively the compressor and the turbine.
Instead, the triggers may be optically detectable surfaces, and the sensors may be optical sensors responsive to the optically detectable triggers to generate signals.
In accordance with a third aspect of this invention, there is provided a method of measuring torque in a rotating shaft, including measuring twist in the rotating shaft in accordance with the first aspect of this invention, and calculating torque on the basis of the measured twist bearing in mind a pre-established length of the shaft aver which length said twist is measured, and pre-established physical characteristics of the shaft determining torque-twist behaviour of the shaft.
Said physical characteristics of the shaft determining torque-twist behaviour of the shaft may advantageously be established empirically.
In accordance with a fourth aspect of this invention, there is provided a measuring apparatus for measuring torque in a rotating shaft, which includes a measuring apparatus for measuring twist in accordance with the second aspect of this invention, in which the processor is programmed to calculate torque on the basis of the measured twist bearing in mind a pre-established length of the shaft over which length said twist is measured and preestablished physical characteristics of the shaft determining torque-twist behaviour of the shaft,
In accordance with a fifth aspect of this invention, there is provided a method of managing operation of an engine including measuring a quantity related to torque in a drive shaft of the engine in accordance with the first aspect or the third aspect of this invention, comparing the measured value of said quantity related to torque to a predetermined standard value of said quantity, establishing any deviation between the measured value and the standard value and controlling an operating function of the engine in response to said establish deviation.
Said operating function of the engine may be at least one of ignition timing when the engine is a spark ignition engine, injector pump timing when said engine is a diesel engine, boost pressure when said engine is turbocharged or supercharged.
Advantageously, the method may include automatically calibrating the measuring apparatus in respect of datum time periods when the engine is operated under a no load condition.
In accordance with a sixth aspect of this invention, there is provided an engine including
a measuring apparatus in accordance with the second aspect or the fourth aspect of this invention;
an engine management apparatus including a comparator arranged to receive a signal indicative of a measured value of a quantity related to torque in a drive shaft of the engine from the measuring apparatus, the comparator being preprogrammed to compare said measured value with a standard value of said quantity related to torque to generate a control signal, the engine management apparatus being responsive to said control signal to control an operating function of the engine.
Said operating function of the engine may be at least one of ignition timing when the engine is a spark ignition engine, injector pump timing when said engine is a diesel engine, boost pressure when said engine is turbocharged or supercharged.
Advantageously, the engine management apparatus may be preprogrammed to calibrate the measuring apparatus in respect of datum time periods when the engine is operated under a no load condition.
The invention will now be described, by way of examples, with reference to the accompanying diagrammatic drawings.